[tor-bugs] #29668 [Core Tor/Tor]: Drop thread_fast_rng during postfork; improve thread_fast_rng fork-safety

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#29668: Drop thread_fast_rng during postfork; improve thread_fast_rng fork-safety
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     Reporter:  nickm         |      Owner:  nickm
         Type:  defect        |     Status:  assigned
     Priority:  Medium        |  Milestone:  Tor: 0.4.1.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:  .1            |   Reviewer:
      Sponsor:                |
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 If you fork with a thread_fast_rng, we need to invalidate the
 thread_fast_rng so it will get reconstructed in the child process.

 We should also tweak thread_fast_rng so that it is always misuse-resistant
 across fork()s in the same way. Right now it has 3 behaviors if you try to
 share it across a fork:
    * it works seamlessly if you have zero-on-fork support
    * it crashes if you have drop-on-fork support
    * it becomes an insecure prng if you have neither.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29668>
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